1. Fieled of the Invention
The present invention concerns a multilayered container made of polyester resins by biaxially orienting blow molding. The invention concerns also the method of making the container. The container according to the present invention has a high anti-gas permeation property and a high bonding strength between the layers.
2. State of the Art
Biaxially oriented shaped articles of polyethylene terephthalate resin (hereinafter referred to as "PET") exhibit good mechanical strength, toughness, heat resistance, chemical resistance, oil resistance and transparency, and are widely used as packaging materials such as films, sheets and containers.
However, containers of PET made by biaxially orienting blow molding have some drawbacks. For example, they cannot be sufficiently heatset, and anti-gas permeation property is dissatisfactory. Particularly, insufficiency of the anti-gas permeation is inherent in PET, and it has been difficult to solve this problem by processing technic.
As a way of improving the anti-gas permeation property of the containers made of PET, it has been tried to laminate PET with a resin having anti-gas permeation property better than that of PET such as poly vinylidene chloride, saponified ethylene-vinyl acetate copolymer and polyamide. All of these resins have poor adhesive property with PET, and therefore, even a three-layered structure with PET on both the sides may be partially delaminated while being subjected to orienting processing or using, and the anti-gas permeation property will decrease.